In the past year, we have demonstrated that MIF and lymphotoxin can be produced by both B- and T-lymphocytes in the quinea pig. Further, using inbred quinea pigs and an Ir gene restriction in strain 13 animals for DNP-PLL, we were able to show that primed B-cells were unable to be activated by antigen directly to produce MIF in the absence of genetically competent T-cells, demonstrating that MIF production by B-cells is a thymus-dependent phenomenon. These results demonstrate the validity of this in vitro assay as a valid measure of T-cell function at the qualitative level; however, since MIF can be produced by both B- and T-lymphocytes, quantitative deductions from in vitro assay about the degree of T-cell involvement cannot be made. In addition, we demonstrated that lymphotoxin production and T-cell cytotoxicity could be totally dissociated by a variety of pharmacologic agents, strongly indicating that the mechanism by which T-cells lyse target cells is not by production of a lymphokine. We have been able to demonstrate that demyelination can occur in the absence of autoimmune sensitization, simply as a non-specific consequence of a specific delayed hypersensitivity reaction to a non-brain antigen occurring in the vicinity of myelinated nerve fibers. Lastly, we have demonstrated that non-specifically activated macrophages, i.e., by BCG priming and challenged, were capable of eliminating infection by a protozoal parasite, Trypanosoma cruzi. Further, we established that the mechanism by which the parasite escapes killing in normal macrophages is to escape from the phagocytic vesicles and penetrate into the cytoplasm where macrophages have no specialized mechanism for eliminating them. BIBLIOGRAPHIC REFERENCES: Bloom, Barry R., Stoner, G., Gaffney, J., Shevach, E. and Green, I. Production of MIF and LT by Non T-Cells. European J. of Immunol. 5:218, 1975. Tanowitz, H., Wittner, M., Kress, Y. and Bloom, B.R. Studies on In Vitro Infection by Trypanosoma cruzi: I. Ultrastructural Studies on the Invasion of Macrophages and L-Cells. Amer. J. Trop. Med. 24:25, 1975.